1. Field of the Invention
The present invention relates to an electromagnetic pilot-type clutch device.
2. Description of Related Art
As shown in FIG. 1, in a conventional electromagnetic pilot-type clutch device 10 for starting a vehicle by transmitting rotation power of an engine to a driving wheel, an output shaft 23 is rotatably supported on a rotation axis in a differential case 20 by tapered roller bearings 51, 52. The differential case 20 accommodates a differential gear 29 such as a bevel gear, and a case 11 is fixed to the differential case 20. The case 11 accommodates a housing 13 which is integrally connected to an input shaft 21. The housing 13 has a clutch accommodating chamber 14. An inner shaft 15 extends in the clutch accommodating chamber 14 and is rotatably supported by a bearing 24 and a needle bearing 25. Components such as a main clutch 16, a cam-type amplifying mechanism 18 and a pilot clutch 34 are mounted within the clutch accommodating chamber 14. An opening 64 of the housing 13 is covered by a rear housing 57. In order to maintain a fluid-tight state, oil seals 55, 68 are respectively provided between the outer peripheral surface of the inner shaft 15 and the inner peripheral surface of a smaller-diameter rear housing portion 37 and between the outer peripheral surface of a larger-diameter rear housing portion 38 and the inner peripheral surface of the case 11. An electromagnet 33 is fixed to a yoke 36 so as to face the pilot clutch 34 with the rear housing 57 interposed therebetween. The yoke 36 maintains a small gap between the yoke 36 itself and the smaller-diameter and larger-diameter rear housing portions 37, 38, and rotatably supports the smaller-diameter rear housing portion 37 by a bearing 28. The yoke 36 has a fitted portion 36a and an engaging portion 36b. The fitted portion 36a projects from the opening 64 of the housing 13 and is fittingly supported in a yoke fitting hole 50 of the differential case 20. A pin 47 is provided at an end of the case 11 so as to project from the end face of the case 11. The engaging portion 36b engages with the pin 47 in order to prevent rotation of the yoke 36. Various components are thus mounted within the housing 13 to form a housing assembly 41.
The housing 13 has a shoulder portion 46 in its front part. More specifically, the outer peripheral surface of the housing 13 forms the shoulder portion 46 near the input shaft 21. The shoulder portion 46 is rotatably supported within the case 11 by an outer bearing 65. An oil seal 19 is mounted near the bearing 65 in order to maintain a fluid-tight state of the case 11. The case 11 and the differential case 20 are separated at the end face of the opening 64 of the housing 13. An oil seal 54 is provided between the outer peripheral surface of a protruding end of the smaller-diameter rear housing portion 37 and the inner peripheral surface of the differential case 20 in order to separate the case 11 from the differential case 20 in a fluid-tight manner.
In the above conventional clutch device, the housing assembly is supported both in the case and the differential case. It takes a long time to mount the housing assembly to the case and the differential case. Moreover, if the shape of the housing assembly is changed, the shape of the differential case must also be changed accordingly. Furthermore, the respective central axes of the case and the differential case may be displaced from each other. Such displacement may degrade the fluid-tight property of the oil seal, and also may impede the balanced state of the input shaft and the output shaft within the case. Moreover, the engaging portion of the yoke for preventing rotation may become unstable. In such a case, the housing assembly may vibrate and abnormal noises are generated from the engaging portion due to variation in rotation of components such as the housing.
It is an object of the present invention to provide an electromagnetic pilot-type clutch device that improves mounting of a housing assembly, eliminates unbalanced rotation, and has no adverse effect on vibration of an axle caused by such unbalanced rotation.
In order to achieve the above object, an electromagnetic pilot-type clutch device according to the present invention includes an output shaft, an input shaft, a housing, a rotating member, a main clutch, a pilot clutch, a rear housing, a yoke, and a cam-type amplifying mechanism. The output shaft is rotatably supported on a rotation axis in a differential case accommodating a differential gear. The input shaft is rotatably supported on the rotation axis in a case fixed to the differential case. The housing is provided in the case, integrally connected to the input shaft, and has a clutch accommodating chamber. The rotating member is rotatably supported in the housing, extends in the clutch accommodating chamber, and is detachably connected to the output shaft in a rotatable manner. The main clutch has main outer clutch plates and main inner clutch plates. The main outer clutch plates are engaged with an inner peripheral surface of the clutch accommodating chamber with restriction of relative rotation so as to be movable in an axial direction. The main inner clutch plates are arranged alternately with the main outer clutch plates, and engaged with the rotating member with restriction of relative rotation so as to be movable in an axial direction. The pilot clutch has pilot outer clutch plates and pilot inner clutch plates. The pilot outer clutch plates are engaged with the inner peripheral surface of the clutch accommodating chamber with restriction of relative rotation so as to be movable in an axial direction. The pilot inner clutch plates are arranged alternately with the pilot outer clutch plates, and engaged with a first cam member with restriction of relative rotation so as to be movable in an axial direction. The rear housing is formed by a larger-diameter rear housing portion fixed to the housing, a smaller-diameter rear housing portion rotatably supporting the rotating member, and an annular, non-magnetic intermediate member connecting the larger-diameter and smaller-diameter rear housing portions together at a position facing an armature with the pilot clutch interposed therebetween. The yoke has an electromagnet fixed thereto, and rotatably supports the smaller-diameter rear housing portion by a bearing. The electromagnet is provided between the larger-diameter and smaller-diameter rear housing portions, and attracts the armature to press the pilot outer clutch plates and the pilot inner clutch plates together. The cam-type amplifying mechanism has the first cam member and a second cam member that contacts the main clutch. The cam-type amplifying mechanism allows the second cam member to be moved in an axial direction by a cam mechanism caused by relative rotation of the first and second cam members, thereby amplifying torque transmitted to the pilot clutch in response to attraction of the electromagnet and pressing the main clutch. An outer peripheral surface of the yoke is fitted to the case in a fluid-tight manner so as to prevent rotation of the yoke. An inner peripheral surface of the yoke is fitted to an outer peripheral surface of the smaller-diameter rear housing portion in a fluid-tight manner.
In the above electromagnetic pilot-type clutch device, a housing assembly is prepared as a sub assembly. More specifically, the rotating member, the main clutch, the pilot clutch, the yoke having the electromagnet fixed thereto, the cam-type amplifying mechanism, and the rear housing are mounted in the housing so as to form the housing assembly. The outer peripheral surface of the yoke of the housing assembly is fitted to the case so as to prevent rotation of the yoke. The inner peripheral surface of the yoke is fitted to the outer peripheral surface of the smaller-diameter rear housing portion in a fluid-tight manner by using a seal. The housing assembly is thus supported only in the case. This facilitates mounting of the housing assembly. Moreover, design of the differential case need not be changed even if design of the housing assembly is changed. This enables the use of a differential case having the same design. Furthermore, even if the respective central axes of the case and the differential case are displaced from each other, fluid-tight property of the oil seal will not be degraded, and the input shaft and the output shaft are retained in a well-balanced state. Moreover, the outer peripheral surface of the yoke is fitted to the case so as to be supported therein. As a result, the input shaft and the output shaft will not be rendered in an unbalanced state and vibration will not be caused by the displacement between the central axes of the case and the differential case.
Preferably, an elastic seal member is provided between the yoke and the case and between the yoke and the smaller-diameter rear housing portion.
In the above electromagnetic pilot-type clutch device, the elastic seal members provided between the yoke and the case and between the yoke and the smaller-diameter rear housing portion applies rotation resistance to the yoke. This rotation resistance effectively functions against variation in rotation of the housing assembly or the like. As a result, abnormal noises generated by the portion for preventing rotation of the yoke can be reliably reduced.
Preferably, the case and the differential case are fixed after being positioned by a fitting hole formed concentrically with the rotation axis.
In the above electromagnetic pilot-type clutch device, the case can be stably fitted to the differential case with high accuracy without causing any displacement between the central axes of the case and the differential case.